Calibration and alignment of large zoom lens systems

Le résumé fourni par la source

Four large zoom lens systems are currently being built for x-ray sources.Radiographic imaging needs require 270 mm x 270 mm square scintillators and the capability to use both 92 x 92 mm and 62 x 62 mm CCD cameras.Each zoom lens system incorporates 11 elements and is designed to be almost telecentric in both image and object space.Each zoom lens system images a thick scintillator emitting light peaking at 435 nm, so special glass types are required for the lens elements.Much larger elliptical pellicles are needed to deflect the scintillator light out of the xray path into the zoom lens system.The optical axis of the imaging system must be colinear with the x-ray axis.Two scintillators are positioned on each of two x-ray axes, for a total of four scintillators and four zoom lens systems.An optional configuration will be shown, enabling two lens systems imaging opposite sides of a single scintillator, for a total of four lenses and two scintillators.Although this configuration has advantages, it could suffer from crosstalk.Care must be taken to analyze the anti-reflection coatings applied to all the elements in the imaging chain, including the CCD array and its vacuum window.Design of two-color counter-propagating laser alignment systems will be demonstrated, which shows how the best possible resolution can be achieved.Flip mirrors are used to allow six alignment lasers to have access to the optical axis.Monitoring all retro-reflections at two different wavelengths simplify optical alignment.The evolution of our x-ray radiographic systems over the last two decades will be discussed.

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